Comparative References are usually Visual Standards sometimes called Boundary Samples

Can anyone define was a "comparative reference" is and give examples? The standard calls for control and verification at stated frequency but does not give a clear definition of what exactly a comparative reference is.

Comparitive references are usually visual standards. For example if acceptance or rejection of your product is based on subjective criteria ("good" color vs. "bad" color) you have a representative sample that represents "good" color or acceptable product. That "good" sample would be your "reference sample" to which you would compare finished product.

My examples include:
1) wire harness samples used as guidelines as operators assemble

2) Known non-conforming product (painted red for ID) used for testing mistake-proof devices to ensure they still detect the mistake they are designed to.

3) Known non-conforming product (ID'd as above) used to verify testing machines still fail bad parts as they should.

4) Machined set blocks used to set-up production equipment (including shims)

Is any of this stuff comparative references? Do I have to control any of this stuff? Thanks for any answers!!!
-Diane

1)Yes those are comparative references and,
2)Yes they all must be controlled.